Grey colored heat treatable coated article having low solar factor value

ABSTRACT

There are provided coated articles that include two or more infrared (IR) reflecting layers (e.g., of or including NbZr, Nb, NiCr, NiCrMo, and/or a nitride thereof) sandwiched between at least dielectric layers, and/or a method of making the same. The coating may be designed so that the coated articles realize grey (including black) glass side reflective coloration in combination with a low solar factor (SF) and/or a low solar heat gain coefficient (SHGC). Such coated articles may be used in the context of monolithic windows, insulating glass (IG) window units, laminated windows, and/or other suitable applications, and may optionally be heat treated (e.g., thermally tempered) in certain instances.

This application claims priority on U.S. Provisional Application62/308,439, filed Mar. 15, 2016, which is incorporated herein byreference.

This invention relates to coated articles that include two or morefunctional infrared (IR) reflecting layers sandwiched between at leastdielectric layers, and/or a method of making the same. The coating maybe designed so that the coated articles realize grey glass sidereflective coloration in combination with a low solar factor (SF) and/orlow solar heat gain coefficient (SHGC). Such coated articles may be usedin the context of monolithic windows, insulating glass (IG) windowunits, laminated windows, and/or other suitable applications, and mayoptionally be heat treated (e.g., thermally tempered) in certaininstances.

BACKGROUND AND SUMMARY OF THE INVENTION

Solar control coatings having a layer stack of glass/Si₃N₄/NiCr/Si₃N₄are known in the art, where the metallic NiCr layer is the sole infrared(IR) reflecting layer in the coating. In certain instances, the NiCrlayer may be nitrided. For example, see U.S. Pat. No. 6,926,967, whichis hereby incorporated herein by reference. See also U.S. Pat. No.5,688,585.

Unfortunately, while such layer stacks with NiCr IR reflecting layersprovide efficient solar control and are overall good coatings, they arelacking in terms of being able to achieve a wider palette of availablecolors when desired. For example, with such a coating stack, if bluishgreen is desired the approach is to significantly increase the bottomdielectric thickness which unfortunately results in undesirableinterference effects in that particular coating.

Grey (including black) coloration is sometimes desired in the context ofmonolithic windows, insulating glass (IG) window units, and/or othersuitable applications. Desirable grey (including black) coloration(e.g., glass side reflective, or exterior), measured monolithicallyand/or in an IG window unit, may be characterized by: a* values of from−3.0 to +5.0, more preferably from −2.0 to +4.0, and most preferably−1.0 to +3.0; in combination with b* values of from −10.0 to +2.0, morepreferably from −9.0 to −1.0, and most preferably from −4.0 to −8.0; incombination with a glass side reflective/exterior L* value of from20-42, more preferably from 23-35, and most preferably from 25-33; incombination with a visible transmission (TY or T_(vis)) of no greaterthan 16%.

Low solar factor (SF) and solar heat gain coefficient (SHGC) values arealso desired in some applications, particularly in warm weatherclimates. Solar factor (SF), calculated in accordance with EN standard410, relates to a ratio between the total energy entering a room or thelike through a glazing and the incident solar energy. Thus, it will beappreciated that lower SF values are indicative of good solar protectionagainst undesirable heating of rooms or the like protected bywindows/glazings. A low SF value is indicative of a coated article(e.g., IG window unit) that is capable of keeping a room fairly cool insummertime months during hot ambient conditions. Thus, low SF values aresometimes desirable in hot environments. While low SF values aresometimes desirable for coated articles such as IG window units, theachievement of lower SF values may come at the expense of sacrificingcoloration. It is often desirable, but difficult, to achieve acombination of acceptable visible transmission, desirable glass sidereflective coloration, and a low SF value for a coated article such asan IG window unit or the like. SF (G-Factor; EN410-673 2011) and SHGC(NFRC-2001) values are calculated from the full spectrum (T, Rg and Rf)and are typically measured with a spectrophotometer such as a PerkinElmer 1050. The SF measurements are done on monolithic coated glass, andthe calculated values can be applied to monolithic, IG and laminatedapplications.

U.S. Patent Document 2012/0177899 discloses several different coatings.The Examples 1, 4 and 5 on page four of U.S. '899 in [0026] areglass/SiN/NiCrNx/SiN/NiCrNx/SiN. However, these examples haveundesirable green or bronze glass side reflective coloration.Unfortunately, all Examples in U.S. '899 suffer from undesirably high SFand SHGC values as well as high visible glass side reflectivity over20%.

U.S. Pat. No. 8,286,395 discloses numerous examples in columns 5-7,including examples of glass/SiN/NbN/SiN/NbN/SiN. Unfortunately, theexamples of U.S. '395 are unable to achieve desirable grey glass sidereflective color as defined above. For instance, all examples in U.S.'395 have a visible transmission of at least 20%. Moreover, U.S. '395 issilent as to SF and SHGC values, as well as L* values. It is noted thatglass side reflective color is a significant color when an IG windowunit is provided with the coating on surface two, as the glass sidereflective color is the color seen by those outside viewing the buildingon which the window is mounted.

It would be desirable if grey glass side reflective coloration could beachieved in combination with low SF and/or SHGC value(s). Note that atypical conventional IG window unit with two panes has an SHGC valuearound 0.70.

In certain example embodiments of this invention, it has surprisinglybeen found that by providing two or more IR reflecting layers (e.g., ofor including NbZr and/or NbZrN_(x)) between respective dielectriclayers, along with particular thickness parameters, desirable grey glassside reflective coloration can be achieved in combination with low SFand/or SHGC value(s). And optionally these desirable features may beachieved in combination with heat treatability and/or low visible glassside reflectivity. Such coatings provide for improved color controland/or ranges when desired, low SF values and thus the ability to keeprooms cool in warm climates, and also for good thermal stability (lowΔE* value(s)) if desired.

Generally speaking, certain example embodiments of this inventionfulfill one or more of the above listed needs by providing a coatedarticle having grey glass side reflective coloration and including alayer system supported by a glass substrate, the layer systemcomprising: a first dielectric layer comprising nitrogen; a firstinfrared (IR) reflecting layer on the glass substrate over at least thefirst dielectric layer; a second dielectric layer comprising nitrogen onthe glass substrate over at least the first dielectric layer and thefirst IR reflecting layer; a second layer IR reflecting layer on theglass substrate over at least the second dielectric layer; a thirddielectric layer comprising nitrogen on the glass substrate over atleast the second IR reflecting layer; wherein each of the first andsecond IR reflecting layers comprises one or more of: NbZr, NbZrN_(x),NiCr, NiCrN_(x), NiCrMo, NiCrMoN_(x), NbCr, NbCrN_(x), Nb and NbN_(x);and wherein the coated article has: glass side/exterior reflective greycoloration comprising a glass side/exterior reflective a* value of from−3.0 to +5.0, a glass side/exterior reflective b* value of from −10.0 to+2.0, a glass side/exterior reflective L* value of from 20-42, and avisible transmission of no greater than 16%, and wherein: (i) ifmeasured monolithically has an SF value of no greater than 0.33 and anSHGC value of no greater than 0.39, and/or (ii) if an insulating glass(IG) window unit having two glass substrates has an SF value of nogreater than 0.23 and an SHGC value of no greater than 0.27.

Certain example embodiments of this invention fulfill one or more of theabove listed needs by providing a coated article having grey glass sidereflective coloration and including a layer system supported by a glasssubstrate, the layer system comprising: a first dielectric layercomprising silicon nitride; a first infrared (IR) reflecting layercomprising NbZr on the glass substrate over at least the firstdielectric layer comprising silicon nitride; a second dielectric layercomprising silicon nitride on the glass substrate over at least thefirst dielectric layer comprising silicon nitride and the first IRreflecting layer comprising NbZr; a second layer IR reflecting layercomprising NbZr on the glass substrate over at least the seconddielectric layer comprising silicon nitride; a third dielectric layercomprising silicon nitride on the glass substrate over at least thesecond IR reflecting layer comprising NbZr; and wherein the coatedarticle has: glass side/exterior reflective grey coloration comprising aglass side/exterior reflective a* value of from −3.0 to +5.0, a glassside/exterior reflective b* value of from −10.0 to +2.0, a glassside/exterior reflective L* value of from 20-42, and a visibletransmission of no greater than 16%, and: (i) if measured monolithicallyhas an SF value of no greater than 0.33 and an SHGC value of no greaterthan 0.39, and/or (ii) if an insulating glass (IG) window unit havingtwo glass substrates has an SF value of no greater than 0.23 and an SHGCvalue of no greater than 0.27.

Thus, this invention covers monolithic window units, IG window units,laminated window units, and any other article including a glasssubstrate having a coating thereon as claimed. Note that monolithicmeasurements may be taken by removing a coated substrate from an IGwindow unit and/or laminated window unit, and then performing monolithicmeasurements. It is also noted that for a given coating the SF and SHGCvalues will be significantly higher for a monolithic window unit thanfor an IG window unit.

In certain example embodiments of this invention, heat treated (HT)coated articles have a glass side reflective ΔE* value due to heattreatment (e.g., thermal tempering) of no greater than 4.5, morepreferably no greater than 4.0, even more preferably no greater than3.5, and most preferably no greater than 3.0. For purposes of example,the heat treatment (HT) may be for at least about 5 minutes at atemperature(s) of at least about 580 degrees C., and is sufficient forthermal tempering. The term ΔE* is known in the art and is indicative ofthermal stability upon heat treatment, and is defined and explained forexample in U.S. Pat. No. 6,926,967 which is incorporated herein byreference.

IN THE DRAWINGS

FIG. 1 is a partial cross sectional view of a monolithic coated article(heat treated or not heat treated) according to an example embodiment ofthis invention.

FIG. 2 is a partial cross sectional view of a monolithic coated article(heat treated or not heat treated) according to another exampleembodiment of this invention.

FIG. 3 is a side cross sectional view of an insulating glass (IG) windowunit, including the coated article of FIG. 1 or FIG. 2, according toexample embodiments of this invention.

DETAILED DESCRIPTION OF CERTAIN EXAMPLE EMBODIMENTS OF THE INVENTION

Referring now more particularly to the accompanying drawings in whichlike reference numerals indicate like parts throughout the severalviews.

Coated articles according to example embodiments of this inventionachieve desirable grey (including black) glass side reflectivecoloration in combination with low SF and/or SHGC value(s), andoptionally also achieve heat treatability and/or visible glass sidereflectivity of no greater than 20% (more preferably no greater than15%, and most preferably no greater than 8%). It has surprisingly beenfound that by providing two or more IR reflecting layers (e.g., of orincluding NbZr and/or NbZrN_(x)) between respective dielectric layers,along with particular thickness parameters, desirable grey glass sidereflective coloration can be achieved in combination with a low SFand/or SHGC value(s). And optionally these desirable features may beachieved in combination with heat treatability and/or visible glass sidevisible reflectivity (R_(G[or outside, or exterior])Y) of no greaterthan 20% (more preferably no greater than 15%, and more preferably nogreater than 8%). In example embodiments of this invention, the coatedarticle: (i) if measured monolithically has an SF value of no greaterthan 0.33 (more preferably no greater than 0.32, and most preferably nogreater than 0.31) and/or an SHGC value of no greater than 0.39, morepreferably no greater than 0.37, and most preferably no greater than0.35, and/or (ii) if an insulating glass (IG) window unit having twoglass substrates has an SF value of no greater than 0.23 (morepreferably no greater than 0.22, and most preferably no greater than0.21) and/or an SHGC value of no greater than 0.27 (more preferably nogreater than 0.25, and most preferably no greater than 0.23). Thus, suchcoatings provide for improved color control and/or ranges when desiredand low SF values indicating ability to keep rooms cool in warmenvironments, and may also provide for good thermal stability (low ΔE*value(s)) when desired.

Certain embodiments of this invention provide a coating or layer systemthat may be used in windows such as monolithic windows (e.g., vehicle,residential, and/or architectural windows), IG window units, and/orother suitable applications. Certain example embodiments of thisinvention provide a layer system that is characterized by color control,low SF values, and/or color stability upon heat treatment. With respectto stability upon heat treatment (HT), this means a low value of ΔE*;where A is indicative of a*, b* and L* change in view of HT such asthermal tempering, heat bending, or thermal heat strengthening,monolithically and/or in the context of dual pane environments such asIG units or laminates. In certain exemplary embodiments, the colorstability with HT may result in substantial matchability betweenheat-treated and non-heat treated versions of the coating or layersystem. In other words, in monolithic and/or IG applications, in certainembodiments of this invention two glass substrates having the samecoating system thereon (one HT after deposition and the other not HT)appear to the naked human eye to look substantially the same.

The terms “heat treatment” and “heat treating” as used herein meanheating the article to a temperature sufficient to achieve thermaltempering, heat bending, and/or heat strengthening of the glassinclusive article. This definition includes, for example, heating acoated article in an oven or furnace at a temperature of least about 580degrees C., more preferably at least about 600 degrees C., for asufficient period to allow tempering, bending, and/or heatstrengthening. In certain instances, the HT may be for at least about 4or 5 minutes. The coated article may or may not be heat treated indifferent embodiments of this invention.

FIGS. 1-2 are side cross sectional views of coated articles according todifferent example embodiments of this invention. In the FIG. 1embodiment the solar control coating 8 includes two IR reflecting layers3 and 5, whereas in FIG. 2 the solar control coating 8′ includes threeIR reflecting layers 3, 5 and 15. An additional dielectric layer 16 isalso provided in the FIG. 2 embodiment. FIG. 3 illustrates an IG windowunit, with the coating (8 or 8′) on surface two, showing that the IGwindow unit can use the coating (8 or 8′) of either the FIG. 1embodiment or the FIG. 2 embodiment.

Referring to FIG. 1, the coated article includes at least glasssubstrate 1 (e.g., clear, green, bronze, grey, blue, or blue-green glasssubstrate from about 1.0 to 12.0 mm thick), dielectric layers 2, 4, 6(e.g., of or including silicon nitride (e.g., Si₃N₄), siliconoxynitride, tin oxide, or some other suitable dielectric), IR reflectinglayers 3, 5 which may be of or include substantially metallic ormetallic material such as NbZr, NbZrN_(x),, NiCr, NiCrN_(x), NiCrMo,NiCrMoN_(x), NbCr, NbCrN_(x), Nb and/or NbN_(x). It will be appreciatedthat the IR reflecting layers 3 and/or 5 may optionally be nitrided incertain example embodiments of this invention. While the IR reflectinglayers may include some small amount of oxygen in certain instances, itis preferable that these layers 3 and 5 are substantially free of oxygensuch as no more than 5% oxygen, more preferably no more than about 3% or2% oxygen in certain embodiments (atomic %). The coated article furtherincludes dielectric overcoat layer 7 of or including a protectivematerial such as zirconium oxide (e.g., ZrO₂) or silicon oxynitride.Optionally, a dielectric layer of or including silicon oxynitride and/orzirconium silicon oxynitride of any suitable stoichiometry may belocated between and contacting layers 6 and 7 in the upper part of thelayer stack. In certain example embodiments of this invention, coating 8does not include any metallic IR blocking or reflecting layer of orbased on Ag or Au. In certain example embodiments of this invention, IRreflecting layers 3 and 5 reflect at least some IR radiation, and do notcontact any other metal IR reflecting layer. In certain exampleembodiments, it is possible for each of the layers to include othermaterials such as dopants. It will be appreciated of course that otherlayers may also be provided, or certain layers may be omitted, anddifferent materials may be used, in certain alternative embodiments ofthis invention.

Referring to the FIG. 2 embodiment, the coated article includes at leastglass substrate 1 (e.g., clear, green, bronze, grey, blue, or blue-greenglass substrate from about 1.0 to 12.0 mm thick), dielectric layers 2,4, 6, 16 (e.g., of or including silicon nitride (e.g., Si₃N₄), siliconoxynitride, tin oxide, or some other suitable dielectric), IR reflectinglayers 3, 5, 15 which may be of or include substantially metallic ormetallic material such as NbZr, NbZrN_(x), NiCr, NiCrN_(x), NiCrMo,NiCrMoN_(x), NbCr, NbCrN_(x), Nb and/or NbN_(x). It will be appreciatedthat the IR reflecting layers 3, 5 and/or 15 may optionally be nitridedin certain example embodiments of this invention. Optionally, adielectric layer of or including silicon oxynitride and/or zirconiumsilicon oxynitride of any suitable stoichiometry may be located betweenand contacting layers 16 and 7 in the upper part of the layer stack inthe FIG. 2 embodiment. While the IR reflecting layers may include somesmall amount of oxygen in certain instances, it is preferable that theselayers 3, 5, 15 are substantially free of oxygen such as no more than 5%oxygen, more preferably no more than about 3% or 2% oxygen in certainembodiments. The coated article in FIG. 2 further includes dielectricovercoat layer 7 of or including a protective material such as zirconiumoxide (e.g., ZrO₂) or silicon oxynitride. For example, when the IRreflecting layers are of or include NbZr, they may be sputter depositedusing NbZr targets, and with a gas flow of from about 200-300 ml Ar andfrom about 0.8-2.5 ml/kW N₂ and/or O₂.

In certain example embodiments of this invention, coating 8′ of the FIG.2 embodiment does not include any metallic IR blocking or reflectinglayer of or based on Ag or Au. In certain example embodiments of thisinvention, IR reflecting layers 3, 5 and 15 reflect at least some IRradiation, and do not contact any other metal IR reflecting layer. Incertain example embodiments, it is possible for each of the layers toinclude other materials such as dopants. It will be appreciated ofcourse that other layers may also be provided, or certain layers may beomitted, and different materials may be used, in certain alternativeembodiments of this invention.

The overall coatings (8, 8′) of FIGS. 1-2 include at least theillustrated layers. It is noted that the terms “oxide” and “nitride” asused herein include various stoichiometries. For example, the termsilicon nitride (for one or more of layers 2, 4, 6, 16) includesstoichiometric Si₃N₄, as well as non-stoichiometric silicon nitride.Likewise, various stoichiometries may be used. For instance, when NbZris used for IR reflecting layers 3, 5, 15, various ratios of Nb to Zrmay be used including but not limited to a 50/50 ratio, an 85/15 ratio,or a 90/10 ratio. In certain example embodiments of this invention, theNb/Zr ratio in layers 3, 5, and 15 may be from 1/1 to 9.5/1 in variousexample embodiments of this invention, such that these layers preferablycontain more Nb than Zr. The illustrated layers may be deposited onglass substrate 1 via magnetron sputtering, any other type ofsputtering, or via any other suitable technique in different embodimentsof this invention. It is noted that other layer(s) may be provided inthe stacks shown in FIGS. 1-2 such as between layers 2 and 3, or betweenlayers 3 and 4, or between the substrate 1 and layer 2, or the like.Generally, other layer(s) may also be provided in other locations of thecoating. Thus, while the coating 8, 8′ or layers thereof is/are “on” or“supported by” substrate 1 (directly or indirectly), other layer(s) maybe provided therebetween. Thus, for example, the layer systems 8, 8′ andlayers thereof shown in FIGS. 1-2 are considered “on” the substrate 1even when other layer(s) may be provided therebetween (i.e., the terms“on” and “supported by” as used herein are not limited to directlycontacting). However, there may be the direct contacts shown in FIGS.1-2 in preferred embodiments.

In certain example embodiments of this invention, dielectric layers 2,4, 6, and 16 may each have an index of refraction “n” of from 1.7 to 2.7(at 550 nm), more preferably from 1.9 to 2.5 in certain embodiments, andmost preferably from about 2.0 to 2.06 in preferred embodiments of thisinvention. One, two, three, or all of these layers 2, 4, 6, 16 may be ofor include silicon nitride and/or silicon oxynitride in certain exampleembodiments of this invention. In such embodiments of this inventionwhere layers 2, 4, 6 and/or 16 comprise silicon nitride (e.g., Si₃N₄),sputtering targets including Si employed to form these layers may or maynot be admixed with up to 1-20% (e.g., 8%) by weight aluminum orstainless steel (e.g. SS#316), with about this amount then appearing inthe layers so formed. Even with this amount(s) of aluminum and/orstainless steel, such layers are still considered dielectric layers.

While FIGS. 1-2 illustrate a coated article according to an embodimentof this invention in monolithic form, coated articles according to otherembodiments of this invention may comprise IG (insulating glass) windowunits such as shown in FIG. 3. In IG window embodiments, coating 8 or 8′from FIGS. 1-2 may be provided on the inner wall of the outer substrateof the IG unit as shown in FIG. 3 (surface two), and/or on the innerwall of the inner substrate, or in any other suitable location in otherembodiments of this invention. As shown in FIG. 3, an example IG windowunit may comprise a pair of spaced apart glass substrates 1, 30 eachabout 3-19 mm thick, at least one of which is coated with a coating 8,8′ herein in certain example instances, where the insulating gap 34between the substrates may be from about 5 to 30 mm, more preferablyfrom about 10 to 20 mm, and most preferably about 16 mm. Spacer(s) 32may be provided around the periphery to space the glass substrates fromeach other and maintain gap 34. In certain preferred embodiments, theglass substrate 1 shown in FIGS. 1-2 may be the outer glass substrate 1of an IG window unit as shown in FIG. 3 and the coating 8, 8′ may beprovided on the interior surface of the outer glass substrate 1 (i.e.,surface two of the IG window unit). The gap between substrates in an IGunit may be filed with air and/or argon gas in certain exampleembodiments. IG window units having three glass substrates/panes mayalso be used.

Turning back to the FIG. 1 embodiment, various thicknesses may be usedconsistent with one or more of the needs discussed herein. According tocertain example embodiments of this invention, example thicknesses (inangstroms) and materials for the respective layers of the FIG. 1embodiment on the glass substrate 1 are as follows in certain exampleembodiments for achieving desired grey glass side reflective colorationin combination with a low SF and/or SHGC value(s) (layers are listed inorder moving away from the glass substrate 1):

TABLE 1 (Thicknesses for grey color and low SF/SHGC in FIG. 1embodiment) Example Preferred Layer Range (Å) (Å) Best (Å) siliconnitride (layer 2): 400-1,000 Å 550-850 Å 600-750 Å IR reflector (e.g.,NbZr)   50-140 Å  70-120 Å  80-100 Å (layer 3): silicon nitride (layer4):   300-800 Å 500-700 Å 550-650 Å IR reflector (e.g., NbZr)   50-140 Å 70-120 Å  80-100 Å (layer 5): silicon nitride (layer 6):   150-450 Å250-400 Å 270-310 Å overcoat (e.g., ZrO₂)   10-500 Å  10-60 Å  20-40 Å(layer 7):

Table 1 above relates to, for example, embodiments where glass sidereflective generally grey coloration and a low SF and/or SHGC value(s)are desirable for the FIG. 1 embodiment (or FIG. 1 embodiment used in anIG window unit as shown in FIG. 3). It has been surprisingly found thatin the FIG. 1 embodiment desirable grey glass side reflective colorationcan be achieved in combination with low SF and low SHGC values and lowglass side visible reflection (R_(G/outside/exterior)Y) using thethicknesses discussed in Table 1 above and when designing the FIG. 1coating 8 so that: (i) IR reflecting layers 3 and 5 (e.g., of orincluding NbZr, or a nitride thereof) are of substantially the samethickness, which means that they are the same thickness plus/minus 15 Å,(ii) a thickness ratio of layer 2/layer 6 is at least 1.5, morepreferably at least 2.0, and (iii) a thickness ratio of layer 4/layer 6is at least 1.4, more preferably at least 1.7. It is noted thatdesirable grey (which includes black herein) coloration (e.g., glassside/exterior reflective), measured monolithically and/or in an IGwindow unit, may be characterized by: a* values of from −3.0 to +5.0,more preferably from −2.0 to +4.0, and most preferably −1.0 to +3.0; incombination with b* values of from −10.0 to +2.0, more preferably from−9.0 to −1.0, and most preferably from −8.0 to −4.0; in combination witha glass side reflective/exterior L* value of from 20-42, more preferablyfrom 23-35, and most preferably from 25-33; in combination with avisible transmission (TY or T_(vis)) of no greater than 16% (e.g.,7-16%).

In certain example embodiments, the IR reflecting layers 3 and 5 may beof the same or substantially the same materials as indicated above(e.g., NbZr and/or a nitride thereof). In certain example embodiments,the layers 3 and/or 5 are metallic, or substantially metallic, and areprovided between nitride layers (e.g., silicon nitride based layers 2,4, 6) in order to reduce or prevent oxidation of the IR reflectinglayers during possible heat treatment (e.g., thermal tempering, heatbending, and/or heat strengthening) thereby permitting predictablecoloration to be achieved following the heat treatment at multipleviewing angles.

In certain exemplary embodiments, the color stability with HT may resultin substantial matchability between heat-treated and non-heat treatedversions of the coating or layer system. In other words, in monolithicand/or IG applications, in certain embodiments of this invention twoglass substrates having the same coating system thereon (one HT afterdeposition and the other not HT) appear to the naked human eye to looksubstantially the same.

Before and/or after any optional heat treatment (HT) such as thermaltempering, in certain example embodiments of this invention coatedarticles according to the FIG. 1 (or FIG. 1, 3) embodiment havecolor/optical characteristics as follows in Table 2 (measured monolithicand/or in an IG unit). It is noted that subscript “G” stands for glassside reflective, subscript “T” stands for transmissive, and subscript“F” stands for film side reflective. As is known in the art, glass side(G) means when viewed from the glass side (as opposed to the layer/filmside) of the coated article. Film side (F) means when viewed from theside of the coated article on which the coating is provided. Table 3 setforth below illustrates certain characteristics of coated articlesaccording to certain example embodiments of this invention after HT suchas thermal tempering (monolithically measured for Table 3) for allcolors. The characteristics below in Table 2 are applicable to HT andnon-HT coated articles herein, except that the thermal stability data inTable 3 relates to HT coated articles and demonstrates the stabilityupon HT.

TABLE 2 Color/Optical Characteristics (FIG. 1 embodiment monolithic orin IG) Most General Preferred Preferred T_(vis) (TY): <=16% 6-16%<=7-14% L*_(T) 25-60 35-55 40-50 a*_(T) −8 to +8 −5 to +5 −2 to +2b*_(T) −15 to +15 −10 to +10 −5 to +5 R_(G)Y(glass side): <=20% <=15%<=8% L*_(G) 20-42 23-35 25-33 a*_(G) −3 to +5 −2 to +4 −1 to +3 b*_(G)−10 to +2  −9 to −1 −8 to −4 R_(F)Y(film side): <=35% <=20% <=15% a*_(F)−15 to +15 −8 to +8 −4 to +4 b*_(F) −30 to +30 −22 to +22 −15 to +15R_(s) (Ω/sq): <140 <100 30−75 SF [Monolithic]: <=0.33 <=0.32 <=0.31 SHGC[Monolithic]: <=0.39 <=0.37 <=0.35 SF [IG]: <=0.23 <=0.22 <=0.21 SHGC[IG]: <=0.27 <=0.25 <=0.23

TABLE 3 Thermal Stability (FIG. 1 after HT; in addition to Table 2)General Preferred Most Preferred ΔE*_(G) <=4.0 <=3.5 <=3.0

Regarding the FIG. 2 embodiment, various thicknesses may be usedconsistent with one or more of the needs discussed herein. According tocertain example embodiments of this invention, example thicknesses (inangstroms) and materials for the respective layers of coating 8′ in theFIG. 2 embodiment on the glass substrate 1 are as follows in certainexample embodiments for achieving desired grey glass side reflectivecoloration in combination with a low SF and/or SHGC value(s) (layers arelisted in order moving away from the glass substrate 1):

TABLE 4 (Thicknesses for grey color and low SF/SHGC in FIG. 2embodiment) Example Preferred Layer Range (Å) (Å) Best (Å) siliconnitride (layer 2):  20-250 Å  40-160 Å  60-140 Å IR reflector (e.g.,NbZr) (layer 3):  10-90 Å  10-50 Å  15-40 Å silicon nitride (layer 4):150-800 Å 300-600 Å 350-500 Å IR reflector (e.g., NbZr) (layer 5): 20-150 Å  30-100 Å  40-90 Å silicon nitride (layer 6): 300-900 Å400-750 Å 500-650 Å IR reflector (e.g., NbZr) (layer 15):  14-150 Å 20-100 Å  30-90 Å silicon nitride (layer 16): 100-700 Å 200-570 Å300-470 Å overcoat (e.g., ZrO₂) (layer 7):  10-500 Å  10-60 Å  20-40 Å

Table 4 above relates to, for example, embodiments where glass sidereflective generally grey coloration and a low SF and/or SHGC value(s)are desirable for the FIG. 2 embodiment (or FIG. 2 embodiment used in anIG window unit as shown in FIG. 3). It has been surprisingly found thatin the FIG. 2 embodiment desirable grey glass side reflective colorationcan be achieved in combination with low SF and low SHGC values, and lowglass side visible reflection (R_(G/outside/exterior)Y) using thethicknesses discussed in Table 4 above and when designing the FIG. 2coating 8′ so that one or more of the following are satisfied: (i) IRreflecting layers 5 and 15 (e.g., of or including NbZr, or a nitridethereof) are of substantially the same thickness, which means that theyare the same thickness plus/minus 15 Å, (ii) dielectric layers 4 and 16are of substantially the same thickness, which means that they are thesame thickness plus/minus 10%, (iii) a thickness ratio of layer 6/layer4 is at least 1.1, and (iv) a thickness ratio of layer 6/layer 2 is atleast 2, more preferably at least 3.

In certain example embodiments, the IR reflecting layers 3, 5 and 15 maybe of the same or substantially the same materials as indicated above(e.g., NbZr and/or a nitride thereof). In certain example embodiments,the layers 3, 5 and/or 15 are metallic, or substantially metallic, andare provided between nitride layers (e.g., silicon nitride based layers2, 4, 6, 16) in order to reduce or prevent oxidation of the IRreflecting layers during possible heat treatment (e.g., thermaltempering, heat bending, and/or heat strengthening) thereby permittingpredictable coloration to be achieved following the heat treatment atmultiple viewing angles.

Before and/or after any optional heat treatment (HT) such as thermaltempering, in certain example embodiments of this invention coatedarticles according to the FIG. 2 (or FIG. 2, 3) embodiment havecolor/optical characteristics as follows in Table 5 (measured monolithicand/or in an IG unit). Table 6 set forth below illustrates certaincharacteristics of coated articles according to certain exampleembodiments of this invention after HT such as thermal tempering(monolithically measured for Table 6) for all colors. Thecharacteristics below in Table 5 are applicable to HT and non-HT coatedarticles herein according to the FIG. 2 (or FIG. 2-3) embodiment, exceptthat the thermal stability data in Table 6 relates to HT coated articlesand demonstrates the stability upon HT.

TABLE 5 Color/Optical Characteristics (FIG. 2 embodiment monolithic orin IG) Most General Preferred Preferred T_(vis) (TY): <=16% 6-16% 7-14%L*_(T) 25-60 35-55 40-50 a*_(T) −8 to +8 −5 to +5 −2 to +2 b*_(T) −15 to+15 −10 to +10 −5 to +5 R_(G/outside)Y(glass side): <=20% <=15% <=8  L*_(G) 20-42 23-35 25-33 a*_(G) −3 to +5 −2 to +4 −1 to +3 b*_(G) −10 to+2  −9 to −1 −8 to −4 R_(F/inside)Y(film side): <=35% <=20% <=15% a*_(F)−15 to +15 −8 to +8 −4 to +4 b*_(F) −30 to +30 −22 to +22 −15 to +15R_(s) (Ω/sq): <160 <100 30-75 SF [Monolithic]: <=0.33 <=0.32 <=0.31 SHGC[Monolithic]: <=0.39 <=0.37 <=0.35 SF [IG]: <=0.23 <=0.22 <=0.21 SHGC[IG]: <=0.27 <=0.25 <=0.23

TABLE 6 Thermal Stability (FIG. 2 after HT; in addition to Table 5)General Preferred Most Preferred ΔE*_(G) <=4.0 <=3.5 <=3.0

For purposes of example only, Examples 1-3 representing differentexample embodiments of this invention, as well we Comparative Examples(CEs) 1-2, are set forth below.

EXAMPLES

Examples 1 and 3 were layer stacks on a clear glass substrate as shownin FIG. 1, and Example 2 was a layer stack on a clear glass substrate asshown in FIG. 2. All were measured monolithically, heat treated andmeasured again. They were also put into IG window units as shown in FIG.3. The silicon nitride layers in each example were deposited bysputtering a silicon target (doped with about 8% Al) in an atmosphereincluding argon and nitrogen gas. The glass substrates 1 and 30 wereclear and 6 mm thick, and the air gap 34 in the IG window unit was 12 mmthick. The NbZr layers in each example were deposited by sputteringapproximately 90/10 Nb/Zr magnetron sputtering targets in an atmosphereincluding argon and a small amount of nitrogen gas. Comparative Examples(CEs) 1-2 were provided for purposes of comparison. Layer thicknesseswere in angstroms (A).

TABLE 7 Layer Stacks of Examples Layer Ex. 1 Ex. 2 Ex. 3 CE 1 CE 2silicon nitride (layer 2): 736 Å  79 Å 647 Å 600 Å 1310 Å NbZr (layer3):  91 Å  30 Å  89 Å  68 Å  107 Å silicon nitride (layer 4): 588 Å 397Å 611 Å 314 Å  236 Å NbZr (layer 5):  88 Å  74 Å  84 Å 136 Å n/a siliconnitride (layer 6): 298 Å 570 Å 283 Å 388 Å n/a NbZr (layer 15): n/a  72Å n/a n/a n/a silicon nitride (layer 16): n/a 382 Å n/a n/a n/a ZrO₂(layer 7):  30 Å  30 Å  30 Å  40 Å  40 Å

Measured monolithically before tempering (HT), Examples 1-3 according toembodiments of this invention and Comparative Examples (CEs) 1-2 had thefollowing characteristics (annealed and non-HT, monolithic) (I11. C, 2degree observer). Note that “R_(G)Y (at angle of 45°)” indicates visibleglass side reflection at an angle of forty-five degrees from normal.

TABLE 8 Measured Monolithic, annealed (before tempering) Parameter Ex. 1Ex. 2 Ex. 3 CE 1 CE 2 T_(vis) (TY)(transmission ): 13.3% 13.4% 13.6%19.0% 34.0% a*_(T) 0.9 0.6 1.8 −0.5 2.5 b*_(T) −2.1 −1.4 −1.0 6.5 −8.0R_(G)Y(glass side refl. %):  6.9%  6.3%  5.1% 10.5% 26.0% L*_(G): 31.630.2 27.1 38.7 58.0 a*_(G): 0.7 1.2 1.9 −2.0 −10.0 b*_(G): −5.0 −6.5−6.4 −6.5 3.0 Glass side refl. color: grey grey grey grey greenR_(G)Y(at angle of 45°):  7.5%  7.3% 6.4 n/a n/a R_(F)Y(film side refl.%): 11.4%  7.4% 14.1%  6.0% 15.0% a*_(F): −0.2 −1.7 −1.1 15.0 0.0b*_(F): −5.9 1.3 −6.8 35.0 9.0 SF (EN410-673 2011): 0.296 0.301 0.3170.352 0.513 SHGC (NFRC-2001): 0.340 0.344 0.360 0.405 0.590

It can be seen from Table 8 above that measured monolithically prior toany optional thermal tempering only Examples 1-3 had a combination of(i) desirable grey glass side reflective visible color, (ii) a lowSF/SHGC value(s), and (iii) low glass side visible reflectivity(R_(G)Y). It can be seen above that Comparative Example 2 (CE 2) wasundesirable at least because it could not achieve grey glass sidereflective coloration as defined herein (e.g., note the −10 value fora*_(G), the high L*_(G) value, and the high visible transmission valueof CE 2), and because it had a high glass side reflectivity. And theonly CE that could arguably achieve grey glass side reflective a* and b*values was CE 1, but CE 1 was problematic in that its SF and SHGC valuesare too high and its visible transmission is rather high at 19%, and itsglass side reflectivity (RGY) was also higher than those of Examples1-2. Moreover, the a*F value of CE 1 was rather high. The SF and SHGCvalues of CE 2 are also too high. It can be seen from Table 8 that theSF and SHGC values of Examples 1-3 were improved (lower) compared tothose of CEs 1-2. Thus, it can be seen that by providing two or more IRreflecting layers (e.g., of or including NbZr and/or NbZrN_(x)) betweenrespective dielectric layers, along with particular thicknessparameters, desirable grey glass side reflective coloration can beachieved together with a low SF/SHGC value(s). And optionally thesedesirable features may be achieved in combination with low glass sidereflectivity. Thus, such coatings provide for improved color controland/or ranges when desired and low SF/SHGC values indicating ability tokeep rooms cool in warm environments.

Measured monolithically after tempering (HT), Examples 1-3 according toembodiments of this invention had the following characteristics (HT,monolithic) (I11. C, 2 degree observer). The pre-HT data is provided inTable 9 for CEs 1-2, as it would not have significantly changed due toHT.

TABLE 9 Measured Monolithic, after thermal tempering (HT) for Exs. 1-3Parameter Ex. 1 Ex. 2 Ex. 3 CE 1 CE 2 T_(vis) (TY)(transmission ): 12.9%12.9% 12.6% 19.0% 34.0% a*_(T) 1.3 1.0 1.8 −0.5 2.5 b*_(T) 0.1 0.4 −1.96.5 −8.0 R_(G)Y(glass side refl. %):  5.8%  6.8%  5.2% 10.5% 26.0%L*_(G): 28.9 31.3 27.4 38.7 58.0 a*_(G): 2.2 0.9 1.9 −2.0 −10.0 b*_(G):−5.9 −5.5 −4.5 −6.5 3.0 Glass side refl. color: grey grey grey greygreen R_(G)Y(at angle of 45°):  6.8%  7.8%  6.5% n/a n/a R_(F)Y(filmside refl. %): 13.0%  8.5% 13.8%  6.0% 15.0% a*_(F): −0.8 −1.7 0.1 15.00.0 b*_(F): −4.8 3.9 −5.5 35.0 9.0 SF (EN410-673 2011): 0.308 0.3000.301 0.352 0.513 SHGC (NFRC-2001): 0.352 0.345 0.344 0.405 0.590

It can be seen from Table 9 above that following thermal tempering (HT)only Examples 1-3 had a combination of (i) desirable grey glass sidereflective visible color, (ii) a low SF/SHGC value(s), and (iii) lowglass side visible reflectivity (R_(G)Y). See the discussion above underTable 8 comparing Examples 1-3 with CEs 1-2, which points are applicablehere also.

Measured in an IG window unit as shown in FIG. 3 (with the coating onsurface two) before tempering, Examples 1-3 according to embodiments ofthis invention and Comparative Examples (CEs) 1-2 had the followingcharacteristics (annealed and non-HT, IG unit) (I11. C, 2 degreeobserver).

TABLE 10 IG Window Unit, annealed (before optional tempering) ParameterEx. 1 Ex. 2 Ex. 3 CE 1 CE 2 T_(vis) (TY)(transmission ): 12.2% 12.2%12.8% 17.5% 30.0% a*_(T) 0.3 0.1 1.7 −1.0 2.0 b*_(T) −1.3 −0.6 −1.3 6.5−7.5 R_(G/out)Y(glass side  6.9%  6.6%  5.3% 11.0% 27.0% refl. %):L*_(G): 31.6 30.9 27.6 39.6 59.0 a*_(G): 0.7 1.6 2.0 −2.0 −10.0 b*_(G):−5.2 −6.9 −6.5 −6.0 2.0 Glass side refl. color: grey grey grey greygreen R_(G)Y(at angle of 45°):  7.7%  7.5%  6.5% n/a n/aR_(F/interior)Y(film side 17.0% 13.7% 19.3% 12.0% 20.0% refl. %):a*_(F): −1.9 −2.2 −1.8 6.0 −1.0 b*_(F): −3.4 0.7 −4.3 10.0 5.0 SF(EN410-673 2011): 0.197 0.200 0.216 0.240 0.350 SHGC (NFRC-2001): 0.2280.231 0.250 0.276 0.403

It can again be seen from Table 10 above that measured in an IG windowunit as shown in FIG. 3 prior to any optional thermal tempering onlyExamples 1-3 had a combination of (i) desirable grey glass sidereflective visible color, (ii) a low SF/SHGC value, and (iii) low glassside visible reflectivity (R_(G)Y). It can be seen above thatComparative Example 2 (CE 2) was undesirable at least because it couldnot achieve grey glass side reflective coloration as defined herein(e.g., note the −10 value for a*_(G), the high L*_(G) value, and thehigh visible transmission value of CE 2), and because it had a highglass side reflectivity. And the only CE that could arguably achievegrey glass side reflective a* and b* values was CE 1, but CE 1 wasproblematic in that its SF and SHGC values are too high and its visibletransmission is rather high, and its glass side reflectivity (R_(G)Y)was also higher than those of Examples 1-2. Moreover, the a*_(F) valueof CE 1 was rather high. The SF and SHGC values of CE 2 are also toohigh. It can be seen from Table 8 that the SF and SHGC values ofExamples 1-3 were improved (lower) compared to those of CEs 1-2. Thus,it can be seen that by providing two or more IR reflecting layers (e.g.,of or including NbZr and/or NbZrN_(x)) between respective dielectriclayers, along with particular thickness parameters, desirable grey glassside reflective coloration can be achieved together with a low SF/SHGCvalue(s). And optionally these desirable features may be achieved incombination with low glass side reflectivity and/or desirable film sidecoloration. Thus, such coatings provide for improved color controland/or ranges when desired and low SF/SHGC values indicating ability tokeep rooms cool in warm environments.

Measured in an IG window unit after tempering (HT), Examples 1-3according to embodiments of this invention had the followingcharacteristics (HT, IG unit) (I11. C, 2 degree observer). The pre-HT IGunit data is provided in Table 11 for CEs 1-2, as it would not havesignificantly changed due to HT.

TABLE 11 IG Window Unit, after thermal tempering (HT) for Exs. 1-3Parameter Ex. 1 Ex. 2 Ex. 3 CE 1 CE 2 T_(vis) (TY)(transmission ): 11.5%11.8% 12.0% 17.5% 30.0% a*_(T) 0.1 0.3 1.0 −1.0 2.0 b*_(T) −0.2 −0.3−1.0 6.5 −7.5 R_(G/out)Y(glass side  5.9%  7.0%  5.0% 11.0% 27.0% refl.%): L*_(G): 29.2 31.8 26.7 39.6 59.0 a*_(G): 2.6 1.2 2.5 −2.0 −10.0b*_(G): −7.1 −5.9 −7.0 −6.0 2.0 Glass side refl. color: grey grey greygrey green R_(G)Y(at angle of 45°):  7.0%  7.9%  6.6% n/a n/aR_(F/interior)Y(film side 18.9% 14.5% 19.0% 12.0% 20.0% refl. %):a*_(F): −2.1 −2.4 −2.0 6.0 −1.0 b*_(F): −2.2 1.8 −5.5 10.0 5.0 SF(EN410-673 2011): 0.215 0.211 0.216 0.240 0.350 SHGC (NFRC-2001): 0.2510.243 0.249 0.276 0.403

It can again be seen from Table 11 above that following thermaltempering (HT) in an IG window unit only Examples 1-3 had a combinationof (i) desirable grey glass side reflective visible color, (ii) a lowSF/SHGC value(s), and (iii) low glass side visible reflectivity(R_(G)Y). See the discussions above under Tables 8 and 10 comparingExamples 1-3 with CEs 1-2, which points are applicable here also.

Example 4

Example 4 was similar to Example 2 with respect to the layer stack, asshown in FIG. 2. Example 4 was as follows: glass(5.8 mm clear)/Si3Nx(13nm)/NbZr(1.8 nm)/Si3Nx(47.8 nm)/NbZr(4.1 nm)/Si3Nx(55.5 nm)/NbZr(3.4nm)/Si3N_(x)(44.7 nm)/ZrOx(3 nm). Example 4 has SF and SHGC valuessimilar to Example 2 above, realized glass side reflective grey color,and had the following optical characteristics as coated (prior tothermal tempering): TY 12.5%; a*_(T) 1.0; b*_(T) 1.0; R_(G/out)Y 7.0%;a*_(G)-3.0; R_(F/interior) 8.0%; a*_(F) −3.5; and b*_(F)4.0. Example 4following thermal tempering (heat treatment) had the following opticalcharacteristics: TY 11.5%; a*_(T) 1.0; b*_(T)-1.0; R_(G/out)Y 6.5%;a*_(G) −1.3; b*_(G)-4.5; R_(F/interior) 8.0%; a*_(F)-3.0; and b*_(F)4.0.

It is noted above that one, two or all of IR reflecting layers 3, 5, 15may be of or include NiCrMo and/or NiCrMoN_(x) in certain exampleembodiments of this invention. In such embodiments one, two or all ofthe IR reflecting layers 3, 5, 15 may, for example, be of or include C22or an oxide and/or nitride thereof. Table 12 below shows an examplecomposition of the NiCrMo-based alloy C22.

TABLE 12 NiCrMo based alloy C22 (wt. %) Element Preferred More PreferredExample Ni 40-70%  50-60%    54-58% (e.g., 56%) Cr  5-40%  10-30%  20-22.5% Mo  5-30%  10-20% 12.5-14.5% Fe  0-15%   0-10%     1-5%(e.g., 3%) W  0-15%   0-10%     1-5% (e.g., 3%) Co  0-15%   0-10%    1-5% (e.g., 3%) Si  0-2%   0-1% =<0.2% (e.g., .08%)  Mn  0-3%   0-2% =<1% (e.g., 0.5%) C  0-1%  0-0.5% =<0.1% (e.g., .01%)  V  0-2%   0-1%  =<1% (e.g., 0.35%)

Once given the above disclosure many other features, modifications andimprovements will become apparent to the skilled artisan. Such otherfeatures, modifications and improvements are therefore considered to bea part of this invention, the scope of which is to be determined by thefollowing claims:

What is claimed is:
 1. A coated article having grey glass sidereflective coloration and including a layer system supported by a glasssubstrate, the layer system comprising: a first dielectric layercomprising silicon nitride; a first infrared (IR) reflecting layercomprising NbZr on the glass substrate over at least the firstdielectric layer comprising silicon nitride; a second dielectric layercomprising silicon nitride on the glass substrate over at least thefirst dielectric layer comprising silicon nitride and the first IRreflecting layer comprising NbZr; a second layer IR reflecting layercomprising NbZr on the glass substrate over at least the seconddielectric layer comprising silicon nitride; a third dielectric layercomprising silicon nitride on the glass substrate over at least thesecond IR reflecting layer comprising NbZr; wherein the coated articlehas: glass side/exterior reflective grey coloration comprising a glassside/exterior reflective a* value of from −3.0 to +5.0, a glassside/exterior reflective b* value of from −10.0 to +2.0, a glassside/exterior reflective L* value of from 20-42, and a visibletransmission of no greater than 16%, and wherein the coated article (i)if measured monolithically has an SF value of no greater than 0.33 andan SHGC value of no greater than 0.39, and/or (ii) if an insulatingglass (IG) window unit having two glass substrates has an SF value of nogreater than 0.23 and an SHGC value of no greater than 0.27.
 2. Thecoated article of claim 1, wherein the coated article has a glassside/exterior a* value of from −2.0 to +4.0.
 3. The coated article ofclaim 1, wherein the coated article has a glass side/exterior b* valueof from −9.0 to −1.0.
 4. The coated article of claim 1, wherein thecoated article has a glass side/exterior b* value of from −8.0 to −4.0.5. The coated article of claim 1, wherein the second dielectric layercomprising silicon nitride is located directly between and contactingthe first and second IR reflecting layers comprising NbZr.
 6. The coatedarticle of claim 1, wherein at least one of the first and second IRreflecting layers comprising NbZr are nitrided.
 7. The coated article ofclaim 1, wherein each of the first and second IR reflecting layerscomprising NbZr includes more Nb than Zr based on an atomic percentage.8. The coated article of claim 1, wherein the coated article is heattreated and has a ΔE* value (glass side reflective) of no greater than3.0 after and/or due to heat treatment.
 9. The coated article of claim1, wherein the coated article has a visible transmission of from 6-16%.10. The coated article of claim 1, wherein the coated article has nometallic infrared (IR) reflecting layer based on Ag and/or Au.
 11. Thecoated article of claim 1, wherein at least one of the first and secondlayers IR reflecting layers is/are substantially free of oxygen.
 12. Thecoated article of claim 1, wherein the coating further comprising anovercoat layer comprising an oxide of zirconium.
 13. The coated articleof claim 1, wherein the coated article has a glass side visiblereflection of no greater than 8%.
 14. The coated article of claim 1,wherein the coated article has a film side/interior reflective a* valueof from −4.0 to +4.0.
 15. The coated article of claim 1, wherein thecoating includes only two IR reflecting layers and consists essentiallyof the first dielectric layer comprising silicon nitride, the firstinfrared (IR) reflecting layer comprising NbZr, the second dielectriclayer comprising silicon nitride, the second layer IR reflecting layercomprising NbZr, and third dielectric layer comprising silicon nitride,and optionally an overcoat layer comprising an oxide of zirconium. 16.The coated article of claim 1, wherein the first and second IRreflecting layers are of substantially the same thickness, which meansthat they are the same thickness plus/minus 15 Å.
 17. The coated articleof claim 1, wherein a thickness ratio of the first dielectriclayer/third dielectric layer is at least 1.5, more preferably at least2.0.
 18. The coated article of claim 1, wherein a thickness ratio of thesecond dielectric layer/third dielectric layer 6 is at least 1.4, morepreferably at least 1.7.
 19. The coated article of claim 1, wherein thecoating further comprises: a third IR reflecting layer comprising NbZron the glass substrate over at least the third dielectric layercomprising silicon nitride; and a fourth dielectric layer comprisingsilicon nitride on the glass substrate over at least the third IRreflecting layer comprising NbZr.
 20. The coated article of claim 1,wherein the coated article (i) if measured monolithically has an SFvalue of no greater than 0.32 and an SHGC value of no greater than 0.37,and/or (ii) if an insulating glass (IG) window unit having two glasssubstrates has an SF value of no greater than 0.22 and an SHGC value ofno greater than 0.25.
 21. A coated article having grey glass sidereflective coloration and including a layer system supported by a glasssubstrate, the layer system comprising: a first dielectric layercomprising nitrogen; a first infrared (IR) reflecting layer on the glasssubstrate over at least the first dielectric layer; a second dielectriclayer comprising nitrogen on the glass substrate over at least the firstdielectric layer and the first IR reflecting layer; a second layer IRreflecting layer on the glass substrate over at least the seconddielectric layer; a third dielectric layer comprising nitrogen on theglass substrate over at least the second IR reflecting layer; whereineach of the first and second IR reflecting layers comprises one or moreof: NbZr, NbZrN_(x), NiCr, NiCrN_(x), NiCrMo, NiCrMoN_(x), NbCr,NbCrN_(x), Nb and NbN_(x); wherein the coated article has: glassside/exterior reflective grey coloration comprising a glassside/exterior reflective a* value of from −3.0 to +5.0, a glassside/exterior reflective b* value of from −10.0 to +2.0, a glassside/exterior reflective L* value of from 20-42, and a visibletransmission of no greater than 16%, and wherein the coated article (i)if measured monolithically has an SF value of no greater than 0.33 andan SHGC value of no greater than 0.39, and/or (ii) if an insulatingglass (IG) window unit having two glass substrates has an SF value of nogreater than 0.23 and an SHGC value of no greater than 0.27.